package com.hxm.demo.kaoshi;

class Test{
	public static void main(String[] args) {
		Singleton instance1 = Singleton.getInstance();
		Singleton instance2 = Singleton.getInstance();
		System.out.println(instance1 == instance2);
	}
}



class Singleton {

	private static volatile Singleton instance;
	
	private Singleton() {}

	public static Singleton getInstance() {
		if(instance == null) {
			synchronized (Singleton.class){
				if (instance == null){
					instance = new Singleton();
				}
			}
		}
		return instance;
	}
}